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In computer science, a for-loop or for loop is a control flow statement for specifying iteration. Specifically, a for-loop functions by running a section of code repeatedly until a certain condition has been satisfied. For-loops have two parts: a header and a body. The header defines the iteration and the body is the code executed once per ...
A shell script can provide a convenient variation of a system command where special environment settings, command options, or post-processing apply automatically, but in a way that allows the new script to still act as a fully normal Unix command. One example would be to create a version of ls, the command to list files, giving it a shorter ...
The example ~/.bash_profile below is compatible with the Bourne shell and gives semantics similar to csh for the ~/.bashrc and ~/.bash_login. The [ -r filename ] && cmd is a short-circuit evaluation that tests if filename exists and is readable, skipping the part after the && if it is not.
A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting language , and is used by the operating system to control the execution of the system using shell scripts .
The Bourne shell (sh) is a shell command-line interpreter for computer operating systems.It first appeared on Version 7 Unix, as its default shell. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic link or hard link to a compatible shell—even when other shells are used by most users.
The S-Lang programming library was started in 1992 by John E. Davis, considering that functions he wrote for a text editor might be useful in other programs. [5] The earliest version of the library contained input/output routines for interacting with computer terminals and an implementation of a simple stack-based interpreter with a PostScript-like syntax that he developed for use in a ...
A shell script (or job) can report progress of long running tasks to the interactive user. Unix/Linux systems may offer other tools support using progress indicators from scripts or as standalone-commands, such as the program "pv". [52] These are not integrated features of the shells, however.
In computer programming, foreach loop (or for-each loop) is a control flow statement for traversing items in a collection. foreach is usually used in place of a standard for loop statement . Unlike other for loop constructs, however, foreach loops [ 1 ] usually maintain no explicit counter: they essentially say "do this to everything in this ...